electrode

Abstract

An electrode (1) according to the present invention is sequentially provided with a base material (2), a conductive carbon layer (4) and a metal layer (5) toward one side in the thickness direction. The conductive carbon layer (4) contains sp2 bonded atoms and sp3 bonded atoms. The metal layer (5) is arranged on one surface (41) of the conductive carbon layer (4) in the thickness direction. The area ratio of the metal layer (5) in the surface (41) of the conductive carbon layer (4) is 95% or less.

Description

Technical Field

[0001] The present invention relates to an electrode.

Background Art

[0002] An electrode including a carbon substrate and a noble metal layer covering one surface of the carbon substrate in an island shape is known (see, for example, Patent Document 1 below). The electrode of Patent Document 1 is used for detecting a physiologically active substance containing glucose.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on the use and purpose of the electrode, a high signal-background ratio is required. The signal-background ratio is the ratio of the signal intensity to the background (noise) intensity. However, in the electrode described in Patent Document 1, there is a limit to increasing the signal-background ratio.

[0005] The present invention provides an electrode having a high signal-background ratio.

Means for Solving the Problems

[0006] The present invention (1) includes a substrate, a conductive carbon layer, and a metal layer provided in this order toward one side in the thickness direction, and the conductive carbon layer contains atoms bonded by sp 2 bonding and atoms bonded by sp 3 bonding, the metal layer is disposed on one surface of the conductive carbon layer in the thickness direction, and the area ratio of the metal layer on the one surface of the conductive carbon layer is 95% or less.

[0007] The present invention (2) includes the electrode described in (1), wherein the metal layer is a gold layer.

[0008] The present invention (3) includes the electrode described in (1) or (2), wherein the metal layer has an island-like structure.

[0009] The present invention (4) is sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The electrode includes one of the items (1) to (3), wherein the ratio of the number of bonding atoms is 0.30 or more.

[0010] The present invention (5) includes an electrode according to any one of (1) to (4), wherein the area ratio described above is 70% or more.

[0011] The present invention (6) further includes an electrode according to any one of (1) to (5), wherein the substrate, the metal substrate, the conductive carbon layer, and the metal layer are arranged sequentially toward one side in the thickness direction.

[0012] The present invention (7) includes an electrode according to any one of claims (1) to (6), wherein the substrate is a flexible film. [Effects of the Invention]

[0013] The electrodes of the present invention have a high signal-to-background ratio. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view of one embodiment of the electrode of the present invention. [Modes for carrying out the invention]

[0015] 1. One embodiment of an electrode An embodiment of the electrode of the present invention will be described with reference to Figure 1. The electrode 1 has thickness. The electrode 1 extends in the planar direction. The planar direction is perpendicular to the thickness direction. Specifically, the electrode 1 has a sheet shape. The electrode 1 comprises a base material 2, a metal underlayer 3, a conductive carbon layer 4, and a metal layer 5 in order toward one side in the thickness direction. In this embodiment, the electrode 1 preferably comprises only the base material 2, the metal underlayer 3, the conductive carbon layer 4, and the metal layer 5.

[0016] 1.1 Base material 2 The substrate 2 forms the other surface of the electrode 1 in the thickness direction. Examples of materials for the substrate 2 include inorganic materials and organic materials. Examples of inorganic materials include silicon and glass. Examples of organic materials include polyester, polyolefin, acrylic, and polycarbonate. Examples of polyester include polyethylene terephthalate (PET) and polyethylene naphthalate.

[0017] Preferably, the material of the base material 2 is an organic material, more preferably polyester, and even more preferably PET. If the material of the base material 2 is an organic material, the base material 2 is a flexible film. If the base material 2 is a flexible film, the electrode 1 has excellent handling properties. The thickness of the base material 2 is, for example, 2 μm or more, preferably 20 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less.

[0018] 1.2 Metal base layer 3 The metal underlayer 3 is disposed on one surface of the base material 2 in the thickness direction. Specifically, the metal underlayer 3 is in contact with one surface of the base material 2 in the thickness direction. The metal underlayer 3 extends in the plane direction. Examples of the material of the metal underlayer 3 include Group 4 metal elements (titanium and zirconium), Group 5 metal elements (vanadium, niobium, and tantalum), Group 6 metal elements (chromium, molybdenum, and tungsten), Group 7 metal element (manganese), Group 8 metal element (iron), Group 9 metal element (cobalt), Group 10 metal elements (nickel and platinum), Group 11 metal element (gold), Group 12 metal element (zinc), Group 13 metal elements (aluminum and gallium), and Group 14 metal elements (germanium and tin). These materials can be used alone or in combination. Preferably, titanium is mentioned as the material of the metal underlayer 3. The thickness of the metal underlayer 3 is 50 nm or less, preferably 35 nm or less, and for example, 1 nm or more, preferably 3 nm or more.

[0019] 1.3 Conductive Carbon Layer 4 The conductive carbon layer 4 is disposed on one surface of the metal underlayer 3 in the thickness direction. Specifically, the conductive carbon layer 4 is in contact with one surface of the metal underlayer 3 in the thickness direction. The conductive carbon layer 4 extends in the plane direction. The conductive carbon layer 4 has conductivity.

[0020] In the present invention, the conductive carbon layer 4 has sp 2 bonded atoms and sp 3 bonded atoms. Specifically, the conductive carbon layer 4 includes carbon with sp 2 bond and carbon with sp 3 bond. That is, the conductive carbon layer 4 has a graphite-type structure and a diamond structure. Thereby, the conductive carbon layer 4 has good conductivity and can increase the signal-background ratio.

[0021] On the contrary, the conductive carbon layer 4 contains sp 2 bonded atoms, but sp 3If the configuration does not include bonding atoms, the signal-to-background ratio cannot be sufficiently high.

[0022] In the conductive carbon layer 4, sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 ) is not limited. In the conductive carbon layer 4, sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 For example, the value is 0.05 or higher, preferably 0.10 or higher, more preferably 0.15 or higher, even more preferably 0.20 or higher, particularly preferably 0.25 or higher, most preferably 0.30 or higher, and also, for example, 0.90 or lower, preferably 0.75 or lower, more preferably 0.50 or lower, even more preferably 0.40 or lower.

[0023] sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 If the above-mentioned lower limit is above, the signal-to-background ratio can be increased. This is presumed to be because the background current decreases as the amount of functional groups on one side 41 of the conductive carbon layer 4 decreases.

[0024] sp 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 ) is measured using X-ray photoelectron spectroscopy.

[0025] Furthermore, the conductive carbon layer 4 is permitted to contain trace amounts of unavoidable impurities other than oxygen.

[0026] The thickness of the conductive carbon layer 4 is, for example, 0.1 nm or more, preferably 1 nm or more, and 100 nm or less, preferably 50 nm or less.

[0027] 1.4 Metal layer 5 The metal layer 5 is positioned on a portion of one surface 41 of the conductive carbon layer 4 in the thickness direction. The metal layer 5, together with the conductive carbon layer 4, forms one surface of the electrode 1 in the thickness direction. The metal layer 5 also exposes the remaining portion of one surface 41 of the conductive carbon layer 4. The metal layer 5, together with the conductive carbon layer 4, forms one surface of the electrode 1 in the thickness direction.

[0028] In this invention, the area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 is 95% or less.

[0029] On the other hand, if the area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 exceeds 95%, the metal layer 5 has a continuous film structure that is continuous in the planar direction, and the electrode 1 cannot obtain a high signal-to-background ratio.

[0030] On the other hand, in this embodiment, since the area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 is 95% or less, the metal layer 5 has an island-like structure, and the electrode 1 can obtain a high signal-to-background ratio.

[0031] Examples of materials for the metal layer 5 include gold, copper, platinum, iron, tin, and silver. Preferably, the material for the metal layer 5 is gold. When the material for the metal layer 5 is gold, the metal layer 5 is a gold layer. When the metal layer 5 is a gold layer, the signal-to-background ratio can be made even higher.

[0032] The area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 is preferably 94% or less, more preferably 93% or less. Furthermore, the area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 is, for example, 10% or more, preferably more than 50%, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 90% or more.

[0033] If the area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 is below the upper limit and above the lower limit described above, the electrode 1 can obtain an even higher signal-to-background ratio.

[0034] The area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 is calculated from the phase image obtained by tapping mode measurement using an atomic force microscope. The method for measuring the area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 will be described in detail in a later example.

[0035] The method for setting the area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 within the above range is not limited. For example, the sputtering time (described later) can be adjusted.

[0036] The metal layer 5 described above has, for example, an island-like structure when viewed from one side in the thickness direction. Specifically, the metal layer 5 contains a large number of independent spherical gold particles dispersed within it. In this case, when the electrode 1 is viewed from one side in the thickness direction, the electrode 1 has a sea-island-like structure.

[0037] The thickness of the metal layer 5 is, for example, 0.05 nm or more, preferably 0.1 nm or more, more preferably 0.3 nm or more, even more preferably 0.7 nm or more, particularly preferably 1 nm or more, most preferably 1.5 nm or more, and even more preferably 2 nm or more, and also, for example, 5 nm or less.

[0038] The thickness of electrode 1 is, for example, 2 μm or more, preferably 20 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less.

[0039] 1.5 Method for manufacturing electrode 1 Next, the manufacturing method for electrode 1 will be described. In this method, first, a substrate 2 is prepared, and then a metal underlayer 3, a conductive carbon layer 4, and a metal layer 5 are formed sequentially on one side in the thickness direction relative to the substrate 2.

[0040] To form the metal underlayer 3 on one surface of the substrate 2 in the thickness direction, for example, a dry method, preferably sputtering, is used. In sputtering, for example, the above-mentioned metal is used as the target. The target has a surface. In sputtering, for example, a noble gas, preferably argon, is used as the sputtering gas. The power applied to the target and the pressure of the sputtering gas are set as appropriate. Specifically, the power density applied to the target is, for example, 1 W / cm². 2 Preferably, 2 W / cm 2 That's all, and also, for example, 5 W / cm 2 The following applies:

[0041] To form the conductive carbon layer 4 on one side of the metal substrate layer 3 in the thickness direction, for example, a dry method, preferably sputtering, is used. In sputtering, for example, carbon is used as the target. The target has a surface. In sputtering, for example, a noble gas, preferably argon, is used as the sputtering gas. The power applied to the target and the pressure of the sputtering gas are set as appropriate. Specifically, the power density applied to the target is, for example, 1 W / cm². 2 Preferably, 2 W / cm 2 That's all, and also, for example, 5 W / cm 2 The following applies:

[0042] To form the metal layer 5 on a portion of one surface 41 of the conductive carbon layer 4 in the thickness direction, for example, a dry method, preferably sputtering, is used. In sputtering, for example, the above-mentioned metal (preferably gold) is used as the target. The target has a surface. In sputtering, for example, a noble gas, preferably argon, is used as the sputtering gas. The pressure of the sputtering gas is set as appropriate. The power density applied to the target is, for example, 1 W / cm². 2 Preferably, 0.5 W / cm 2 More preferably, 0.3 W / cm² 2 The following, and more preferably, 0.2 W / cm 2 The following applies, and also, for example, 0.01 W / cm². 2 Preferably, 0.05 W / cm² 2 That concludes the explanation. The ratio of the power density applied to the metal (preferably gold) target to the power density applied to the metal layer 5 material (preferably gold) is, for example, 0.0001 or more, preferably 0.001 or more, and also, for example, 0.1 or less, preferably 0.05 or less.

[0043] 1.7 Applications of Electrode 1 Next, the applications of electrode 1 will be described. Electrode 1 can be used as various types of electrodes, and preferably as an electrode for electrochemical measurements, specifically as a working electrode for cyclic voltammetry (CV), square wave voltammetry (SWV), anodic stripping voltammetry (ASV), and amperometry.

[0044] In particular, this electrode 1 has a high signal-to-background ratio when measuring bioactive substances. Examples of bioactive substances include blood glucose, which contains glucose.

[0045] When electrode 1 is used as a glucose measurement electrode, a known enzyme is placed on one side of electrode 1 in the thickness direction in a known manner to create an enzyme-modified electrode 10.

[0046] 2. Effects of one embodiment In electrode 1, the conductive carbon layer 4 is sp 2 The atoms that bond and sp 3 The conductive carbon layer 4 contains bonding atoms, and the area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 is 95% or less. Therefore, the signal-to-background ratio is high.

[0047] If metal layer 5 is a gold layer, the signal-to-background ratio will be even higher.

[0048] If the metal layer 5 has an island-like structure, the signal-to-background ratio will be even higher.

[0049] sp 3 Number of bonding atoms and sp 2 sp for the sum of the number of bonding atoms 3 If the ratio of bonding atoms is 0.30 or higher, the signal-to-background ratio will be even higher.

[0050] If the area ratio mentioned above is 70% or higher, the signal-to-background ratio will be even higher.

[0051] Furthermore, since electrode 1 is further equipped with a metal underlayer 3, it improves the adhesion of the conductive carbon layer 4 and, if the material of the substrate 2 is polyester (specifically PET), it has the effect of suppressing degassing from the substrate 2.

[0052] Furthermore, in electrode 1, if the substrate 2 is a flexible film, it offers excellent handling characteristics.

[0053] 3. Variations In the modified examples, components and processes similar to those in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted. Furthermore, the modified examples can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modified examples can be combined as appropriate.

[0054] Although not shown in the diagram, the electrode 1 may comprise two metal underlayment layers 3, two conductive carbon layers 4, and two metal layers 5. Specifically, the electrode 1 of this modified example comprises a metal layer 5, a conductive carbon layer 4, a metal underlayment layer 3, a substrate 2, another metal underlayment layer 3, a conductive carbon layer 4, and a metal layer 5, arranged in order toward one side in the thickness direction.

[0055] Although not shown in the diagram, electrode 1 does not have a metal underlayer 3. In this modified example, the conductive carbon layer 4 is arranged on one side of the substrate 2 in the thickness direction. [Examples]

[0056] The present invention will be further described below with reference to examples and comparative examples. However, the present invention is not limited in any way to the examples and comparative examples. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than or equal to") of the blending ratios (content ratios), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0057] Examples 1 to 5 and Comparative Example 1 A substrate (flexible film) 2 made of PET was prepared.

[0058] On the substrate 2, a 7nm thick metal underlayer 3 made of titanium, a 10nm thick conductive carbon layer 4, and a 0.5-10nm thick metal layer 5 were sequentially formed on one side in the thickness direction using a DC magnetron sputtering apparatus.

[0059] The sputtering conditions for the metal underlayer 3, the conductive carbon layer 4, and the metal layer 5 are shown in Table 1. The area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 was adjusted by the sputtering time.

[0060] In each of the conductive carbon layers 4 of Examples 1 to 4 and Comparative Example 1, sp 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 ) was 0.30. On the other hand, in the conductive carbon layer 4 of Example 5, sp 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 The ratio was 0.35. The above ratio was measured using X-ray photoelectron spectroscopy (XPS, Shimadzu Corporation).

[0061] This resulted in the manufacture of an electrode 1 comprising a base material 2, a metal underlayer 3, a conductive carbon layer 4, and a metal layer 5, arranged sequentially along one side in the thickness direction.

[0062] Comparative Example 2 Electrode 1 was manufactured in the same manner as in Example 1, except that the electrode 1 did not have a metal layer 5.

[0063] Comparative Example 3 sp 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2 Using HOPG (highly oriented pyrolysis graphite, manufactured by Momentive, grade ZYA) with a 0.00 saturation ratio as the substrate, a metal layer 5 (gold layer) with a thickness of 0.5 nm was formed on one side of the substrate by sputtering.

[0064] Comparative Example 4 sp 3 The ratio of the number of atoms to bond (sp 3 / sp 3 +way 2Using HOPG (highly oriented pyrolysis graphite, manufactured by Momentive, grade ZYA) with a 0.00 ratio as the substrate, a 1 nm thick metal layer 5 (gold layer) was formed on one side of the substrate by sputtering.

[0065] <Rating> The following physical properties were evaluated for electrode 1 in each example and comparative example. The results are shown in Table 3.

[0066] (1) Area ratio of the metal layer 5 on one side 41 of the conductive carbon layer 4 The area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 was calculated from the phase image obtained by tapping mode measurement using an atomic force microscope (AFM, Bruker). The image range was defined as minimum phase difference to maximum phase difference. In this phase image, the bright areas were defined as the metal layer 5 and the dark areas as the conductive carbon layer 4. The image was binarized by brightness using image analysis software (WinROOF). The brightness distribution of the image was obtained, and the image was binarized by defining the area up to 70% of the maximum brightness of the bright area as the gold region and the darker area as the conductive carbon region. Using the software, the area ratio of the metal layer 5 on one surface 41 of the conductive carbon layer 4 was calculated from the obtained binarized image.

[0067] (2) Measurement of signal-to-background ratio in glucose response (2-1) Enzyme modification First, an enzyme solution was prepared by mixing 0.8 mg of glucose dehydrogenase, 1.5 μL of 4 wt% bovine serum albumin aqueous solution, 1.2 μL of 1% glutaraldehyde aqueous solution, and 0.3 μL of 0.05 M potassium phosphate buffer (pH 6.5).

[0068] Next, an insulating tape with a 2 mm diameter hole was attached to one side of electrode 1 in the thickness direction to prepare electrode 1 with a known area. The enzyme solution was dropped onto electrode 1 and stored in a refrigerator at 3°C ​​overnight or longer to prepare the enzyme-modified carbon electrode 10.

[0069] (2-2) Measurement of glucose response current First, a 100 mM potassium ferrocyanide solution, an electrolyte solution prepared by adding KCl to 0.05 M phosphate buffer (pH 6.5) to make a total of 1 M, and a 1000 mg / dL glucose solution were mixed according to the formulations in Table 2 to prepare a 0 mg / dL glucose solution and a 600 mg / dL glucose solution, respectively.

[0070] Next, an enzyme-modified carbon electrode 10 was used as the working electrode and connected to a potentiostat (IVIUM Technologies, pocketSTAT) along with a reference electrode (Ag / AgCl) and a counter electrode (Pt) to create an electrochemical measurement system. Then, 1 mL of glucose solution of each concentration was spread on the enzyme-modified carbon electrode 10 for 1 minute. Subsequently, cyclic voltammetry (CV) measurements were performed on the reference electrode of these electrochemical measurement systems with a scanning speed of 0.1 V / sec within a potential sweep range of -0.2 to 0.8 V. From the CV measurement results, the signal-to-background ratio was defined as the value of the current value for a glucose concentration of 600 mg / dl at 0.3 V relative to the current value for a glucose concentration of 0 mg / dl.

[0071] (3) Measurement of the thickness of the metal layer 5 The thickness of metal layer 5 (gold layer) was measured using an X-ray fluorescence analyzer (XRF, Rigaku). The intensity of gold X-ray fluorescence (Au-Lα line) was measured, and the thickness of the gold layer was calculated from this intensity using the following formula. Gold layer thickness = (Gold X-ray fluorescence intensity - 0.0055) / 0.1579

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims below. [Industrial applicability]

[0076] electric Electrodes used for vapor chemistry measurements are, for example, used as working electrodes. [Explanation of Symbols]

[0077] 1 electrode 2 Base material 3 Metal base layer 4. Conductive carbon layer 41 One side of the conductive carbon layer 5 metal layer

Claims

1. The substrate, the conductive carbon layer, and the metal layer are arranged in order toward one side in the thickness direction. The conductive carbon layer is sp ２ The atoms that bond and sp ３ Includes atoms that bond, The metal layer is arranged on one side of the conductive carbon layer in the thickness direction, An electrode in which the area ratio of the metal layer on one side of the conductive carbon layer is 95% or less.

2. The electrode according to claim 1, wherein the metal layer is a gold layer.

3. The electrode according to claim 1 or 2, wherein the metal layer has an island-like structure.

4. sp ３ Number of bonding atoms and sp ２ sp for the sum of the number of bonding atoms ３ The electrode according to claim 1 or 2, wherein the ratio of the number of atoms to bond is 0.30 or more.

5. The electrode according to claim 1 or 2, wherein the area ratio is 70% or more.

6. Furthermore, it is equipped with a metal underlayer, The electrode according to claim 1 or 2, wherein the substrate, the metal underlayer, the conductive carbon layer, and the metal layer are arranged in order toward one side in the thickness direction.

7. The electrode according to claim 1 or 2, wherein the substrate is a flexible film.

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